Along with development of a communication technology, an Evolved Packet System (EPS) is further provided on the basis of a 3rd Generation Partnership Project (3GPP) communication system. An EPS includes an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) and an Evolved Packet Core Network (EPC).
An EPC includes a Home Subscriber Server (HSS), a Mobility Management Entity (MME), a Serving General Packet Radio Service (GPRS) Support Node (SGSN), a Policy and Charging Rule Function (PCRF), a Serving Gateway (S-GW), a Packet Data Network Gateway (P-GW) and a Packet Data Network (PDN).
An EPS usually serves as an intermediate node for communication between two pieces of equipment. Both communication UE accesses the EPS, and implements communication through relay of the EPS. Along with development of communication technology, a Device to Device (D2D) service for direct communication between two adjacent UEs emerges, and the D2D service is also called as a ProSe. In D2D service, two UEs which are close to each other may directly communicate with each other, and data transmitted by equipment may be directly transmitted without returning to a core network. D2D communication may reduce circuitous routing of data on one hand, and may also reduce network data load on the other hand.
FIG. 1 is a structure diagram of a communication system for a D2D service. The communication system includes two UEs performing D2D communication, i.e. UE1 and UE2 respectively. Each UE may access an EPC only through an E-UTRAN, and each UE may belong to the same Public Land Mobile Network (PLMN) or belong to two PLMNs respectively. A PLMN corresponding to one UE may be a Home PLMN (HPLMN) or a Visited PLMN (VPLMN) that the UE accesses from another PLMN. The PLMN of an area where the UE is currently located on may be generally referred to as a Local PLMN (LPLMN), no matter whether the LPLMN is an HPLMN or a VPLMN. In order to implement a D2D discovery service, an operator side not only deploys an EPS, but also includes a ProSe Application (APP) server for deploying the D2D discovery service. The ProSe APP server may be provided by a service provider operating a D2D service, and may also be provided by a network operator operating the EPS. ProSe key management functions are also deployed in different PLMNs. For two UEs of a ProSe service, one UE acquires a service code which may be announced after acquiring a service identifier from the ProSe key management function. The UE becomes Announcing UE (A-UE), and the other UE accepts announcement from the A-UE and matches the ProSe key management function of the A-UE. If the matching is successful, the UE executes the ProSe service with the A-UE. Accordingly, the non-announcing UE becomes a Monitoring UE (M-UE).
In FIG. 1, UE1 is positioned in its HPLMN, and UE2 temporally roams in a VPLMN that UE2 is visiting. The UE provides related ProSe APPs, a connecting interface connecting to the ProSe APP server is the interface of PC1, and a related authentication function is acquired through PC1.
An interface between UEs is PC5, and is configured for direct discovery and communication between UEs.
Interfaces between the UE and the ProSe key management functions are PC3, and are configured to pass discovery authentication of a network.
Interfaces between the ProSe key management function and an existing EPC is PC4, include a user plane interface with a P-GW and a control plane interface with an HSS, and are configured for discovery authentication of a D2D discovery service.
Interfaces between a ProSe key management function and the ProSe APP server are PC2, and are configured for APP implementation of the D2D discovery service.
There are interfaces PC6 and PC7 between a ProSe key management function and another ProSe key management function respectively, and they are configured for the two conditions of roaming and non-roaming of the UE respectively. Interface PC7 is adopted when the UE roams, and interface PC6 is adopted when the UE does not roam, and the two interfaces are configured for information interaction between two ProSe key management functions during the D2D discovery service of the UE.
During specific D2D communication, a UE is required to acquire some information about communication from a ProSe key management function, and performs communication according to the information. However, the UE may not normally perform D2D communication sometimes when the UE has received related information of D2D communication sent from the ProSe key management function, and as a result the D2D communication failed. Particularly in a one-to-many D2D communication process, such a phenomenon is more obvious.